import org.omg.PortableInterceptor.INACTIVE;

import java.util.*;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: Solitudefire
 * Date: 2022-08-02
 * Time: 16:38
 */
public class TopK {
    /**
     * 求数组当中的前K个最小的元素
     *
     * @param array
     * @param k
     * @return
     */
    public static int[] topK(int[] array, int k) {
        //1、创建一个大小为K的大根堆
        PriorityQueue<Integer> maxHeap = new PriorityQueue<>(k, new Comparator<Integer>() {
            @Override
            public int compare(Integer o1, Integer o2) {
                return o2 - o1;
            }
        });
        //遍历数组当中的元素，前K个元素放到队列当中
        for (int i = 0; i < array.length; i++) {
            if (maxHeap.size() < k) {
                maxHeap.offer(array[i]);
            } else {
                //3、从第K+1个元素开始，每个元素与堆顶元素进行比较
                int top = maxHeap.peek();
                if (top > array[i]) {
                    //3.1 先弹出
                    maxHeap.poll();
                    //3.2 后存入
                    maxHeap.offer(array[i]);
                }
            }
        }
        int[] tmp = new int[k];
        for (int i = 0; i < k; i++) {
            tmp[i] = maxHeap.poll();
        }
        return tmp;
    }

    public static void main(String[] args) {
        int[] array = {18, 21, 8, 10, 34, 12};
        int[] tmp = topK(array, 3);
        System.out.println(Arrays.toString(tmp));
    }

    public List<List<Integer>> kSmallestPairs(int[] nums1, int[] nums2, int k) {
        PriorityQueue<List<Integer>> maxHeap = new PriorityQueue<>(k, new Comparator<List<Integer>>() {
            @Override
            public int compare(List<Integer> o1, List<Integer> o2) {
                return (o2.get(0) + o2.get(1)) - (o1.get(0) + o1.get(1));
            }
        });
        for (int i = 0; i < Math.min(nums1.length, k); i++) {
            for (int j = 0; j < Math.min(nums2.length, k); j++) {
                if (maxHeap.size() < k) {
                    List<Integer> tmpList = new ArrayList<>();
                    tmpList.add(nums1[i]);
                    tmpList.add(nums2[j]);
                    maxHeap.offer(tmpList);
                } else {
                    int top = maxHeap.peek().get(0) + maxHeap.peek().get(1);
                    if (top > nums1[i] + nums2[j]) {
                        maxHeap.poll();
                        List<Integer> tmpList = new ArrayList<>();
                        tmpList.add(nums1[i]);
                        tmpList.add(nums2[j]);
                        maxHeap.offer(tmpList);
                    }
                }
            }
        }
        List<List<Integer>> ret = new ArrayList<>();
        for (int i = 0; i < k && !maxHeap.isEmpty(); i++) {
            ret.add(maxHeap.poll());
        }
        return ret;
    }
}
